JPH11194166A - Pulse compression radar system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pulse compression radar system which is improved in distance measuring accuracy and target detecting ability. SOLUTION: A pulse compression radar system is provided with a travel speed extracting means 51 to find the travel speed of a target from pulse compression data and also a chirp signal factor calculating means 52 and a pulse compression factor calculating means 53 to set the optimum chip system so that pulse compression losses may become the minimum in accordance with the travel speed of the target and to calculate the optimum chirp signal factor and pulse compression factor based on the set chirp system.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a pulse compression radar device used for detecting a target such as an aircraft.

[0002]

2. Description of the Related Art In recent years, various types of radar devices have been developed, and one of them is called a pulse compression radar. This is a radar apparatus that transmits a long pulse to suppress the peak power and also compresses the peak power at the time of reception to secure the resolution.

The principle of the pulse compression radar will be described with reference to FIG. The transmission pulse is subjected to frequency modulation that changes linearly with time as shown in FIG. 6A, and is converted into a linear FM pulse as shown in FIG.

When a reception signal corresponding to such a transmission signal is passed through a circuit network having a frequency-to-delay time characteristic as shown in FIG. 6 (c), the frequency components dispersed in the pulse in order are concentrated at one point. And on a steep impulse. Such an operation is called pulse compression (chirp), and the compressed pulse waveform is as shown in FIG. At this time, the amplitude at the peak value is (TΔf) ^1/2 and the pulse width is 1 /
Δf.

The above method is called a linear chirp method. There is also a non-linear chirp system in which the modulation frequency does not change linearly with time.

The linear chirp method is suitable for measuring a distance to a target moving at high speed, and the non-linear chirp method is suitable for measuring a distance to a target moving at low speed. The segregation also depends on the distance to the target. Therefore, at the time of actual distance measurement, the optimal chirp method is selected according to the distance to the target or the moving speed of the target, and the chirp signal coefficient, which is an amount related to the frequency modulation processing, and the pulse compression processing, Optimally setting the pulse compression factor, which is a quantity, is important to minimize measurement errors.

As shown in FIG. 6D, a weak noise component appears near the main pulse compression waveform. That is, when the pulse compression processing is performed, a range side lobe occurs. By setting the optimal chirp signal coefficient and pulse compression coefficient, this range side lobe can be suppressed to a minimum, and as a result, the measurement error can also be minimized.

[0008]

However, the conventional pulse compression radar device has a function of optimally setting the chirp signal coefficient and the pulse compression coefficient according to the distance to the target or the moving speed of the target. Absent. For this reason, accurate distance measurement can be performed only for targets in a very narrow range or a very narrow speed range, and accurate measurements for targets in other wide ranges or speed ranges. Had the disadvantage that it could not be performed.

Further, the pulse compression radar is often used for detecting a target such as an aircraft or an obstacle to the aircraft by utilizing its distance measurement function. However, due to the above-mentioned problem, there is an even worse problem that a target in an extremely narrow range and speed range can be detected.

[0010] The present invention has been made in view of the above circumstances,
An object of the present invention is to provide a pulse compression radar system that improves the accuracy of distance measurement and thereby improves the ability to detect a target.

[0011]

In order to achieve the above object, the present invention transmits a pulse signal subjected to frequency modulation processing based on a chirp signal coefficient toward a target,
In a pulse compression radar device that performs a pulse compression process on the reflected pulse based on a pulse compression coefficient, a target moving speed detecting means for detecting the moving speed of the target, and a target moving speed detected by the target moving speed detecting means. And a coefficient control means for variably controlling the chirp signal coefficient and the pulse compression coefficient in accordance with a moving speed.

More specifically, the coefficient control means minimizes the pulse compression processing loss based on the correspondence between the target moving speed and the pulse compression processing loss related to the pulse compression processing. To this end, the chirp signal coefficient and the pulse compression coefficient are variably controlled.

[0013] More specifically, the coefficient control means includes:
A linear chirp system or a non-linear chirp system, which is a system related to the frequency modulation process, based on a magnitude relationship between a reference speed determined according to a pulse width of a transmitted pulse signal and the target moving speed. And controlling the chirp signal coefficient and the pulse compression coefficient variably to minimize the pulse compression processing loss based on the selected chirp method.

With this configuration, the target moving speed is detected by the target moving speed detecting means. Then, one of the linear chirp system and the non-linear chirp system is selected based on the target moving speed by the coefficient control means, and the pulse compression processing loss is minimized based on the selected chirp system. The chirp signal coefficient and the pulse compression coefficient are set such that

Therefore, regardless of the target moving speed, the pulse compression processing loss can be minimized in the pulse compression processing stage after reception. For this reason, it becomes possible to improve the accuracy of distance measurement.

Further, the present invention is characterized in that a pulse compression coefficient sequence obtained by multiplying a Taylor distribution weight as an amplitude coefficient is used as a pulse compression coefficient in the compression processing.

For example, by using a pulse compression coefficient sequence obtained by multiplying a Taylor distribution weight having a shape (high or low side lobe level) according to a request of a system operator as an amplitude coefficient, a desired pulse compression loss amount is obtained. And the range side lobe level of the pulse compression waveform can be obtained.

Further, according to the present invention, based on a correspondence relationship between a target moving speed and a pulse compression processing loss related to the pulse compression processing, the chirp signal coefficient and the pulse are controlled so as to minimize the pulse compression processing loss. A program for executing a means for determining a compression coefficient, or a method relating to the frequency modulation process, based on a magnitude relationship between a reference speed determined according to a pulse width of a transmitted pulse signal and a moving speed of the target. Linear chirp or non-chirp
Means for selecting one of the linear chirp methods; and determining the chirp signal coefficient and the pulse compression coefficient based on the selected chirp method so as to minimize a pulse compression processing loss associated with the pulse compression processing. And a program for executing the means for executing the program is recorded on a recording medium such as a floppy disk.

By doing so, it becomes easy to widely provide the functional means according to the present invention, and it is possible to facilitate the production of many pulse compression radar devices according to the present invention.

[0020]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a functional block diagram showing a configuration of a pulse compression radar device according to an embodiment of the present invention. The pulse compression radar apparatus of FIG. 1 is realized by a transmission signal generator 1 for generating and outputting a transmission signal modulated based on a given chirp signal coefficient, and amplifying the transmission signal to a transmission level, for example, by a circulator or the like. A transmission device 2 for guiding to a transmission / reception switch (not shown), a reception device 3 for receiving a reception signal (radar echo) given via the transmission / reception switch, and a reception signal output from the reception device 3. On the other hand, a pulse compression process is performed based on a given pulse compression coefficient,
TI (Moving Target Indicator) device (not shown)
And a pulse compressor 4 for guiding to another device, and the presence or absence of a target is detected. Based on the target moving speed, a chirp signal coefficient for the transmission signal generator 1 and a chirp signal coefficient for the pulse compressor 4 are determined. And a target detecting device 5 for giving a pulse compression coefficient.

The transmission signal generator 1 has a chirp signal coefficient table 11, and the chirp signal coefficient given from the target detection device 5 is set in the chirp signal coefficient table 11. Similarly, the pulse compressor 4 includes a pulse compression coefficient table 41, and the pulse compression coefficient given from the target detection device 5 is set in the pulse compression coefficient table 41.

The target detecting device 5 includes a moving speed extracting means 51, a chirp signal coefficient calculating means 52, and a pulse compression coefficient calculating means 53. The moving speed extracting means 51 obtains a target moving speed based on the pulse compression data fed back from the pulse compressor 4, that is, the received signal subjected to the pulse compression processing. In a state where there is no feedback information, for example, immediately after the system is started, the speed information is given from another speed measurement radar (not shown) or a preset value.

The chirp signal coefficient calculating means 52 calculates a chirp signal coefficient related to chirp processing (modulation processing) at the time of transmission based on the target moving speed and a transmission pulse width given from an external device (not shown). I do. The chirp signal coefficient is, specifically, an amount corresponding to the degree of modulation for the transmission signal.

The pulse compression coefficient calculating means 53 similarly calculates
Based on the target moving speed and the transmission pulse width, the calculation of the pulse compression coefficient related to the pulse compression processing at the time of reception is performed. The pulse compression coefficient is an amount corresponding to a compression ratio when compressing the received signal. Here, the transmission pulse width is an amount that can be switched stepwise according to the transmission peak power or the like.

The moving speed extracting means 51, the chirp signal coefficient calculating means 52, and the pulse compression coefficient calculating means 53 are recorded on a recording medium such as a floppy disk or written in advance in a storage device such as a flash memory. This is a processing function that is provided in a degraded state.

Next, the operation of the pulse compression radar apparatus having the above configuration will be described with reference to the flowchart of FIG. In FIG. 2, when the process is started in step ST21, the target detection device 5 determines the target moving speed in step ST22 based on moving speed extracting means or speed information given from outside. In the next step ST23, the target detection device 5 determines the magnitude relation between the reference speed determined according to the pulse width and the target moving speed, based on information indicating the pulse width given from the outside.

The concept of the reference speed will be described with reference to FIG. FIG. 3 is a diagram showing a graph in which the relationship between the target moving speed and the pulse compression processing loss is plotted for the linear chirp system and the non-linear chirp system. Here, the reference speed is shown as an intersection of the graphs of the two chirp systems.

That is, when transmitting a long-distance pulse, the magnitude of the pulse compression processing loss is reversed between the two chirp systems at the speed a as a boundary. Similarly, when transmitting short-range pulses,
The magnitude of the pulse compression processing loss is reversed between the two chirp systems at the speed b. Here, the pulse transmission distance is
Close corresponds to the transmission pulse width.

Now, the target detecting device 5 proceeds to step ST23.
Then, based on the pulse transmission distance corresponding to the pulse width, for example, at the time of long-distance pulse transmission, the magnitude relationship between the target moving speed and the speed a is determined.

Here, when it is determined that the target moving speed is lower than a, the target detecting device 5 proceeds to step ST24 and sets the non-linear chirp system. On the other hand, if it is determined in step ST23 that the target moving speed is higher than a, the target detection device 5 proceeds to step ST2.
The process proceeds to step 5 to set the linear chirp method.

At the time of short-range pulse transmission, the target detecting device 5
Sets any one of the chirp methods through the same process as above, with the reference speed of the magnitude judgment as b.

Next, the target detecting device 5 executes step ST2.
In step 6, the chirp signal coefficient and the pulse compression coefficient corresponding to the target moving speed are determined based on the set chirp method. As described above, the chirp signal coefficient and the pulse compression coefficient are determined.

The determined chirp signal coefficient and pulse compression coefficient are provided to the transmission signal generator 1 and the pulse compressor 4, respectively, and the chirp signal coefficient table 11
And the pulse compression coefficient table 41.

Based on the chirp signal coefficient written in the chirp signal coefficient table 11, the transmission signal generator 1 generates a chirp signal and guides it to the transmitting device 2, and the pulse compression coefficient written in the pulse compression coefficient table 41. The pulse compressor 4 compresses and outputs the received echo based on the coefficient.

By using the chirp signal coefficient and the pulse compression coefficient determined as described above, it is possible to minimize the pulse compression processing loss irrespective of the target moving speed. FIG. 4 shows the effect of the present embodiment. FIG. 4 is a graph in which the response to the distance is plotted, and compared with the pulse compression waveform (reference B) based on the conventional technique, the pulse compression waveform (reference A) according to the present embodiment.
Indicates that the pulse compression processing loss is reduced.

Thus, in this embodiment, the target moving speed is obtained from the pulse compression data by providing the moving speed extracting means 51, and the chirp signal coefficient calculating means 52 and the pulse compression coefficient calculating means 53 are further provided. In order to minimize the pulse compression processing loss in accordance with the above, an optimal chirp scheme is set, and the optimal chirp signal coefficient and pulse compression coefficient are calculated based on the set chirp scheme.

With this configuration, it is possible to minimize the loss of the pulse compression processing regardless of the target moving speed, and to improve the accuracy of distance measurement, thereby improving the target detection capability. .

The present invention is not limited to the above embodiment.

For example, in the above embodiment, the pulse compression processing loss is minimized in order to improve the accuracy of the distance measurement. However, as a more aggressive application, the desired pulse compression loss amount and range sidelobe In order to obtain the pulse compression coefficient, a pulse compression coefficient may be set.

That is, when the target is located at a long distance, since the reception level is low, it is important to suppress the pulse compression processing loss. On the other hand, when the target is located at a short distance, the reception level required for processing as S / N is sufficiently obtained because the reception level is high.

In such a case, in the pulse compression process after reception, a pulse compression coefficient train obtained by multiplying a Taylor distribution weight having a low side lobe level as an amplitude coefficient is used, so that the range of the pulse compression waveform is increased. Side lobes can be suppressed.

FIG. 5 shows the effect when the above processing is performed. It can be seen that the range side lobe is suppressed in the pulse compression waveform (code A) in the case where the above processing is performed as compared with the pulse compression waveform (code B) based on the conventional technology.

In order to obtain a desired amount of pulse compression loss and a range side lobe, not necessarily to suppress the range side lobe, the pulse compression by multiplying the Taylor distribution weight of the side lobe level satisfying them as an amplitude coefficient. A coefficient may be set.

The tailor weight may be set as a pattern in the pulse compression coefficient table 41 in advance.

In addition, various modifications can be made without departing from the gist of the present invention.

[0046]

As described in detail above, according to the present invention,
Providing target moving speed detecting means for detecting the moving speed of the target, obtaining the moving speed of the target, and providing coefficient control means for reducing the chirp signal coefficient and the pulse compression coefficient according to the moving speed of the target to reduce the pulse compression processing loss. Since variable control is provided so as to minimize it, the range side lobe level in the pulse compression process after reception can be suppressed, and the loss of pulse compression processing can be reduced. It is possible to improve accuracy and improve the ability to detect a target.

[Brief description of the drawings]

FIG. 1 is a functional block diagram showing a configuration of a pulse compression radar device according to an embodiment of the present invention.

FIG. 2 shows a target detection device 5 according to the embodiment of the present invention.
5 is a flowchart showing a control procedure of FIG.

FIG. 3 is a diagram showing a pulse compression processing loss of each chirp method with respect to a target moving speed.

FIG. 4 is a diagram showing a manner in which a loss in pulse compression processing is reduced in the embodiment of the present invention.

FIG. 5 is a diagram showing a state in which range side lobes are suppressed in the embodiment of the present invention.

FIG. 6 is a diagram used to explain the principle of a pulse compression radar.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Transmission signal generator 11 ... Chirp signal coefficient table 2 ... Transmission device 3 ... Reception device 4 ... Pulse compressor 41 ... Pulse compression coefficient table 5 ... Target detection device 51 ... Moving speed extraction means 52 ... Chirp signal coefficient calculation means 53 ... Pulse compression coefficient calculating means A ... Pulse compression waveform based on the embodiment of the present invention B ... Pulse compression waveform based on conventional technology

Claims (8)

[Claims] 1. A pulse compression radar device for transmitting a pulse signal subjected to frequency modulation processing based on a chirp signal coefficient to a target, and performing a pulse compression processing on a reflected pulse based on a pulse compression coefficient. Target movement speed detection means for detecting the movement speed of the target, and coefficient control means for variably controlling the chirp signal coefficient and the pulse compression coefficient according to the movement speed of the target detected by the target movement speed detection means. A pulse compression radar device comprising: 2. The method according to claim 1, wherein the coefficient control unit is configured to minimize the pulse compression processing loss based on a correspondence relationship between the target moving speed and a pulse compression processing loss related to the pulse compression processing. 2. The pulse compression radar device according to claim 1, wherein the coefficient and the pulse compression coefficient are variably controlled. 3. A method according to claim 2, wherein said coefficient control means is related to said frequency modulation processing based on a magnitude relationship between a reference speed determined according to a pulse width of a pulse signal to be transmitted and a movement speed of said target. One of a linear chirp method and a non-linear chirp method is selected, and the chirp signal coefficient and the pulse compression coefficient are variably controlled based on the selected chirp method so as to minimize the pulse compression processing loss. The pulse compression radar device according to claim 2, wherein: 4. The pulse compression radar device according to claim 3, wherein a pulse compression coefficient sequence obtained by multiplying a Taylor distribution weight as an amplitude coefficient is used as the pulse compression coefficient in the compression processing. 5. A coefficient determining method in a pulse compression radar device for transmitting a pulse signal subjected to frequency modulation processing based on a chirp signal coefficient to a target and performing a pulse compression processing on a reflected pulse based on a pulse compression coefficient. A first step of detecting the target moving speed; and a correspondence relationship between the target moving speed detected in the first step and a pulse compression processing loss related to the pulse compression processing. And a second step of determining the chirp signal coefficient and the pulse compression coefficient to minimize the pulse compression processing loss. 6. A linear chirp system, which is a system related to the frequency modulation processing, based on a magnitude relationship between a reference speed determined according to a pulse width of a transmitted pulse signal and a moving speed of the target. Or a third step of selecting one of the non-linear chirp methods, wherein the second step minimizes the pulse compression processing loss based on the chirp method selected in the third step. 6. The coefficient determining method according to claim 5, wherein the chirp signal coefficient and the pulse compression coefficient are determined in order to perform the calculation. 7. A coefficient determining method in a pulse compression radar apparatus for transmitting a pulse signal subjected to frequency modulation processing based on a chirp signal coefficient to a target, and applying a pulse compression processing to a reflected pulse based on a pulse compression coefficient. A recording medium storing a program for executing the pulse compression processing loss, based on a correspondence relationship between a target moving speed and a pulse compression processing loss related to the pulse compression processing. A recording medium on which a program for executing means for determining a signal coefficient and the pulse compression coefficient is recorded. 8. A coefficient determining method in a pulse compression radar apparatus for transmitting a pulse signal subjected to frequency modulation processing based on a chirp signal coefficient to a target and applying a pulse compression processing to a reflected pulse based on a pulse compression coefficient. A program related to the frequency modulation process based on a magnitude relationship between a reference speed determined according to a pulse width of a transmitted pulse signal and the target moving speed. Means for selecting one of a linear chirp method and a non-linear chirp method, and the chirp based on the selected chirp method so as to minimize a pulse compression processing loss related to the pulse compression processing. A recording medium recording a program for executing a signal coefficient and a means for determining the pulse compression coefficient.